you're interested in how the mobile version of Firefox is shaping up, you might want to check out a neat video of proposed features released last week.

In the run up to the Firefox 3 launch â€“ get it while it's hot â€“ this little gem seems to have been overwhelmed by the PR exercises and outages its bigger brother has been treated to.

Which is a shame, because the video posted to Aza Raskin's blog last week shows some pretty impressive stuff, albeit in the form of â€œconceptual mockups of an experimental UI for Firefox Mobileâ€ rather than a usable product.

Raskin, the president of user interface design firm Humanized, Inc. and the premier UI expert working at Mozilla Labs, clearly has some excellent ideas on what makes a mobile browser usable. Riffing unashamedly on the features of Mobile Safari, the proposed interface introduces page dragging with intertia (flick the page to one side and it'll skid along even after you've let go, as a piece of paper shoved across a desk would), fluid zooming, minimised controls that allow pages to make the most of the restricted screen real estate, desktop-style tabbed browsing, and something Raskin describes as a â€œspatial view.â€

This last deserves some explanation: when you're zoomed fully out of a page, you'll see pages open in other tabs gathered around you. By dragging these tabs around, you can arrange your open pages in a logical fashion: Raskin uses the example of having â€œa couple pages open to your email, and a couple pages open to some vacation planning materialâ€ and then placing â€œsimilarly-themed sites physically together.â€ Unlike an ordered list of tabs, the 'spatial view' makes the most of our spatial and muscle memories to make finding pages that much easier. At least, that's the theory.

While everyone else is concentrating on optimising their interfaces for multi-touch â€“ again, thank you Apple â€“ Raskin has a different approach. Rather than opt for a multi-touch interface, the designer has decided to go for the lowest-common-denominator angle and ensure his concept for Firefox Mobile operates perfectly on standard single-touch interfaces. He also explains that the demo will run on non-touchscreen devices, but explains that such operation is â€œout of scope for this demo.â€

If you're a bleeding-edge developer eager to get your hands on the shiny new interface toys, you don't even have to wait: while the interface is quite clearly a mock-up, it's not a pre-rendered PR puffery piece. All the code used to create the real-time demo is available on Google Code should you want to have a play.